There has been proposed a three-dimensional random loop bonded structure obtained by forming random loops by curling treatment of a continuous linear structure including a polyester thermoplastic elastic resin, and by making each loop mutually contact in a molten state to weld the majority of contacted parts (Patent Document 1). Also, from the viewpoint of improving lightweight properties, a three-dimensional random loop bonded structure in which the cross sectional structure of a continuous linear structure is a hollow cross section is suggested (Patent Documents 2 and 3). However, there has been a problem in that, when the three-dimensional random loop bonded structure is compressed and recovers its shape, it makes a sound like the random loops being rubbed together or a sound like the random loops being popped, and in the case of being used in bedding, it is loud and interrupts sleep.
In contrast to this, there has been proposed a cushioning material obtained by forming random loops by curling treatment of continuous linear structure including a polyester copolymer and having a fineness of 300 decitex or greater; making each loop mutually contact in a molten state to weld the majority of contacted parts to thereby obtain a three-dimensional random loop bonded structure; and attaching silicone resin to the surfaces of the random loops of the three-dimensional random loop bonded structure (Patent Document 4). However, when the cushioning material is compressed and recovers its shape, although the sound like the random loops being rubbed together is small, the sound like the random loops being popped is still given out. Therefore, there has been room for improvement in terms of quietness. Furthermore, the step of attaching silicone resin to the surfaces of the random loops is a separate step from that for the three-dimensional random loop bonded structure, and also the steps are performed in batches. Therefore, there has been a problem in terms of production.